<h2>DESCRIPTION</h2>

<em>r.param.scale</em> extracts terrain parameters from a digital elevation model. Uses a
multi-scale approach by fitting a bivariate quadratic polynomial to a given
window size using least squares.

<p>The module calculates the following parameters (terminology is from Wood,
1996 with related terminology used in other GRASS modules listed in
brackets):
<ul>
<li>
<i>elev</i>: Generalised elevation value (for resampling purposes at different
scale)</li>

<li>
<i>slope</i>: Magnitude of maximum gradient (steepest slope angle)</li>

<li>
<i>aspect</i>: Direction of maximum gradient (steepest slope direction=flow direction)</li>

<li>
<i>profc</i>: profile curvature (curvature intersecting with the plane
defined by <i>Z</i> axis and maximum gradient direction). Positive values
describe convex profile curvature, negative values concave profile
curvature.</li>

<li>
<i>planc</i>: plan curvature (horizontal curvature, intersecting with
the <i>XY</i> plane)</li>

<li>
<i>longc</i>: longitudinal curvature (profile curvature intersecting
with the plane defined by the surface normal and maximum gradient direction)</li>

<li>
<i>crosc</i>: cross-sectional curvature (tangential curvature intersecting
with the plane defined by the surface normal and a tangent to the contour
- perpendicular to maximum gradient direction)</li>

<li>
<i>maxic</i>: maximum curvature (can be in any direction)</li>

<li>
<i>minic</i>: minimum curvature (in direction perpendicular to the direction
of of maximum curvature)</li>

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<li>
<i>meanc</i> or mean curvature (average of maximum and minimum curvatures).</li>
-->

<li>
<i>feature</i>: Morphometric features: peaks, ridges, passes, channels, pits and planes</li>
</ul>

<h2>NOTES</h2>
In <i>r.param.scale</i> the direction of maximum gradient (considered
downslope) is stored as (West is 0 degree, East is +/- 180 degree):

<ul>
<li>
0..+180 degree from West to North to East</li>

<li>
0..-180 degree from West to South to East</li>
</ul>

Note that the aspect map is calculated differently from
<em><a href="r.slope.aspect.html">r.slope.aspect</a></em>.

<h2>EXAMPLE</h2>

The next commands will create a geomorphological map of the Spearfish sample
dataset region:

<div class="code"><pre>
g.region raster=elevation.10m -p
r.param.scale in=elevation.10m output=morphology method=feature size=9
</pre></div>

<div align="center" style="margin: 10px">
<a href="r_param_scale_morph.jpg">
<img src="r_param_scale_morph.jpg" width="600" alt="r.param.scale example" border=0><br>
</a>
<i>Figure: Geomorphological map of a subregion in the Spearfish (SD) area</i>
</div>


<h2>TODO</h2>

Fix bug when `constrain through central cell' option selected. Create color
tables for all output files (presently only on features).

<h2>REFERENCES</h2>

<ul>
  <li>Wood, J. (1996): The Geomorphological characterisation of
    Digital Elevation Models. Diss., Department of Geography, University
    of Leicester, U.K<br>online at:
    <a href="http://hdl.handle.net/2381/34503">http://hdl.handle.net/2381/34503</a></li>
  <li>Java Code in
    <a href="http://www.geog.le.ac.uk/jwo/research/LandSerf">LandSerf</a>
    that implements the same procedure</li>
</ul>

<h2>SEE ALSO</h2>

<em>
  <a href="r.geomorphon.html">r.geomorphon</a>,
  <a href="r.slope.aspect.html">r.slope.aspect</a>
</em>

<h2>AUTHORS</h2>

<address>
<a href="MAILTO:jwo@le.ac.uk">jwo@le.ac.uk</a>
- <a href="http://www.geog.le.ac.uk/assist/index.html">ASSIST's home</a></address>

<p>Update to FP 3/2002: L. Potrich, M. Neteler, S. Menegon (ITC-irst)

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